The principle of controlling the performance of an engine or other device with respect to a maximum value is known--see the referenced handbook relating to control systems and control steps. The dissertation by Dr. Zechnall discloses the application of control principles to internal combustion engines of the Otto type to control the relative proportion of fuel and air in the fuel-air mixture for maximum performance in accordance with desired characteristics. U.S. Pat. No. 3,142,967, Schweitzer also describes control of extreme values or maxima in connection with internal combustion engines.
The various references disclose the use of controllers having parameters of essentially constant time levels. As a consequence, the adjustment or control speed is always the same, independently of the availability of sensing or measuring data with respect to time. The speed of control in a control loop, and thus the control parameters must be arranged, when applied to internal combustion engines, for low speed of the engine. Low speed of the engine refers to a small or low availability of data and information for any unit of time for the controller. If the engine operates at a higher speed, then the control loop will not adequately follow the performance of the engine since the response speed of the control system will be governed by its initial design--which must also accomodate low speeds. If the response speed of the control system is set to respond quickly, that is, operates best with high engine speeds, then it is possible that, when the engine operates at low speeds, control oscillations or hunting about the desired extreme will result; the amplitude of hunting, that is, the deviation and swing about the desired extreme value can be comparatively large.